Medical Examiner

The Microbes Are Back

What’s behind the Midwest mumps outbreak.

On a winter’s night in 1963, 6-year-old Jeryl Lynn Hilleman shuffled into her father’s bedroom complaining of a sore throat. Her father, Maurice, an eminent virologist at Merck Pharmaceuticals, swabbed his daughter’s throat and drove the cultured Q-tips to his laboratory freezer in West Point, Pa. Four years later, Merck licensed the Jeryl Lynn-strain mumps vaccine. Jeryl Lynn is a biotech executive in California now, but she is unlikely to produce anything as successful as the vaccine that bears her name. Before the vaccine, mumps infected nearly everyone. While usually mild, the virus sometimes caused aseptic meningitis, childhood deafness, and male sterility. The Merck mumps vaccine and others have protected millions of children from the disease and much reduced its repercussions.

No vaccine is perfect, however. The worst mumps epidemic in 17 years is currently sweeping through a heavily vaccinated population in the Midwest. Nearly 1,000 cases have been reported in Iowa since March, and hundreds more in seven other states. A single dose of mumps vaccine—the recommended dosage in Iowa before 1991—protects about 80 percent of those who get it; two doses, the norm today, confers 90 percent immunity. The Iowa outbreak is concentrated in college students, about one-third of whom had not gotten two doses of vaccine as children. Mumps is more serious in older kids and adults—about a fifth of infected men get swollen testicles, as well as the disease’s trademark symptom of a swollen neck; women get sore breasts. Outbreaks in vaccinated populations tend to be less serious, though, and only about 20 people have so far been hospitalized, according to Julie Gerberding, director of the Centers for Disease Control.

The CDC is investigating the origins of the Midwest outbreak. The agency has no clear answers yet, but it may be that these mumps cases are linked to an earlier vaccine scare in Britain. In 1998, gastroenterologist Andrew Wakefield published a report in the medical journal Lancet in which he suggested that the MMR vaccine (called that because mumps protection is nearly always packaged together with vaccines for measles and rubella) caused autism. The article has since been withdrawn and the link between the vaccine and autism disproved. But vaccination rates plunged in the United Kingdom for a few years, resulting in a mumps epidemic of 100,000 cases since 2004. The mumps virus circulating in the Midwest is the same type as the British epidemic strain, though it is too common a variant for scientists to be certain, at this point, of a definitive link.

Importations of viral diseases to the United States from countries with relatively lax vaccination policies are a commonplace. An outbreak of mumps currently sweeping Germany has received far less attention than the Midwest spate of cases, mainly because mumps, measles, and other vaccine-preventable diseases are still routine in Germany and other European countries where vaccination is not mandatory and frequently ignored. The Nietzschean sentiment that sickness makes one stronger is still prevalent in Germany, and kids there are often brought together for “measles parties” so they can get the more definitive immunity that actually catching the unpleasant disease provides.

Germany, Italy, and Japan are the sources of most of the 200 or so cases of imported measles in the United States each year. Japan dropped the MMR vaccine in 1993 because a particular strain of mumps virus used in its vaccine had caused occasional cases of meningitis. The country is negotiating with manufacturers to put together a new MMR vaccine. In the meantime, Japan is a significant source of global measles outbreaks, much to the embarrassment of its health authorities. In the United States, we owe the relative rarity of measles and rubella (a generally trifling viral disease serious only to the fetuses of pregnant women infected with it) to our own vaccine policies—and to the solidarity of our neighbors in Latin America, who have been nearly as zealous as we’ve been in eliminating vaccine-preventable diseases. Still the resurgence of an antique ailment like mumps shows that the battle against microbes continues. It’s a dynamic if not Sisyphean struggle.